Geothermal

Geothermal energy is thermal energy generated and stored in the Earth. Geothermal energy is using hot water or steam from the Earth’s interior for heating buildings or electricity generation.

Geothermal energy is produced from naturally occurring steam and hot water trapped in reservoirs under the surface of the earth (usually about 500 to 2,000 metres below the surface). The energy from this heat can be used directly to heat home or indirectly to generate electricity.

The most common current way of capturing the geothermal energy is to tap into naturally occurring hydrothermal convection systems containing pressurized hot water or steam. These are forced to the surface and used to drive steam turbine generators, or used to heat hot water or air for space or water heating.

Benefits:

• Geothermal power plants do not have to use an intermediate technology to produce steam to power the turbine generators.
• The land needed for geothermal power plants is smaller per megawatt than for almost any other type of power plant.
• Geothermal plants can run 24/7 and are flexible; additional units can be installed as necessary.

Challenges:

• Geothermal energy can only be used in areas where the earth's crust is thin and the steam or hot water sources are close to the surface.
• Sometimes the hot water that is pumped to the surface contains pollutants such as sulphur, which must be removed before using in a power plant.

Global Status and Potential

Geothermal energy is used widely in Iceland, the Philippines, Italy, Indonesia, Mexico, New Zealand, Japan and China. Iceland relies on geysers as its primary source of heat.

The United States is the world's largest producer of geothermal electricity with 2,800 MW in service.

More than 75 countries have geothermal heating capacity; more than 20 have geothermal electricity capacity. More than 1 GW of geothermal power was added to the global renewable energy equation between 2000 and 2004.